This invention relates to surgery and more particularly to improvements in surgical grasping devices, for example forceps and clamps.
It has long been an objective of designers of surgical forceps, clamps and similar instruments to produce an instrument that can grasp slippery tissue securely and yet not cause trauma by puncturing, shearing, stretching or exerting excessive pressure on the tissue. To this end, numerous instruments have been designed having atraumatic toothed jaws made of metal. For an early example, see U.S. Pat. No. 2,668,538, granted on Feb. 9, 1954.
More recently, there has been a trend toward the use of non-metal gripping materials such, as polyvinyldiene fluoride, which are relatively smooth and pliable, but which exhibit sufficiently high friction that they are able to grasp wet, slippery tissue effectively. Such materials are particularly suited to use in disposable attachments to the jaws of grasping instruments, as described in U.S. Pat. No. 5,728,121, dated Mar. 17, 1998.
A trend toward minimally invasive surgery using laparoscopic instruments has given rise to efforts on the part of instrument designers to produce very small instrument jaws and disposable jaw attachments. The jaws and jaw attachments are desirably made as small as possible in size, so that they can pass through small incisions, or through very narrow passages in cannulae used in gaining access to various internal organs, vessels and other tissues.
Heretofore, practical jaw attachments have generally consisted of pliable, tissue-engaging pads mounted on bases of more rigid plastics. The bases have been designed to be removably engaged with instrument jaws, for example by snap-action latching devices which come into locking engagement with the instrument jaws when the attachments are slid into position. It is important that the attachments be very reliable, so that they do not become detached unintentionally and fall into the patient, where their retrieval may be difficult. Designers have encountered a minimum size limit, below which the plastics bases are insufficiently strong to be reliable. Below this minimum size limit, the latch mechanisms of the plastics bases may be inadequate, or the plastics bases may break into pieces. In either case, serious untoward consequences may result.
Alternative attachment base materials, metal, for example are not entirely satisfactory for very small jaw attachments for several reasons. First, when attached to a jaw, they can be quite difficult to remove. Second, unless the metal attachment bases are made to extremely close manufacturing tolerances, they may exhibit some xe2x80x9cplayxe2x80x9d relative to the jaws, which is undesirable, especially in laparoscopic surgery, and are subject to accidental detachment from the jaws.
This invention addresses the above-mentioned problems. Its principal object is to provide a jaw attachment which can be extremely small in size, and yet highly resistant to play, to breakage, and to inadvertent detachment from the instrument jaw on which it is mounted. Other objects of the invention include simplicity, reliability, ease of attachment and detachment, and simplicity of manufacture.
In accordance with the invention, a grasping attachment is removably mounted on at least a first jaw of an instrument having a pair of jaws capable of moving toward and away from each other. The first jaw has a surface facing toward the other jaw, a hole opening to the surface and a clip-engageable portion spaced from the hole. The grasping attachment comprises an assembly of a metal element and a plastics element, and also an elastomeric layer.
The metal element is in the form of a resilient sheet having a plate portion situated in facing relationship to the first jaw, a clip, unitary with the plate portion, and engaged with the clip-engageable portion of the first jaw, and an aperture in the plate portion. The aperture in the plate portion is aligned with the hole in the first jaw.
The plastics element comprises a substantially rigid plastics layer fixed to the plate portion of the metal element, with at least a part of the plate portion located between the plastics layer and the first jaw. The plastics element also has a projection extending from the plastics layer through the aperture in the plate portion. This projection either closely fits into the hole in the first jaw or fits into the hole with a snap fit.
The elastomeric layer is substantially less rigid than the plastics layer, and is secured to the assembly of the metal and plastics elements. At least a portion of the plastics layer is located between the elastomeric layer and the plate portion of the metal element.
The metal element lends strength and stiffness to the grasping attachment, allowing the dimensions of the attachment in the direction perpendicular to the surface of the first jaw to be minimized, and the projection of the plastics layer is sufficiently flexible to fit closely into the aperture of the first jaw without requiring excessively close manufacturing tolerances, or to fit into the aperture with a snap fit.
In a preferred version of the grasping device, the plate portion lies substantially in a plane and is elongated, having first and second ends and opposite longitudinal edges extending from the first end to the second end substantially in the direction of elongation. The clip comprises a pair of ears adjacent to the first end of the plate portion. These ears have first parts extending respectively from the opposite longitudinal edges of the plate portion, out of the plane of the plate portion. The ears also have second parts extending toward each other from the first parts. The second parts overlie the plate portion in spaced relation thereto, and the first jaw is received between the second parts and the plate portion.
The projection, which extends from the plastics layer, through the aperture in the plate portion and into the hole in the first jaw, is located closer to the second end of the plate portion than to the ears of the clip. In one embodiment, at least a portion of the projection extending beyond the plate portion has crushable ribs formed in its exterior wall. The crushable ribs are elongated in directions transverse to the plane of the plate portion, and are deformed by compression when the projection enters the hole in the jaw. The crushable ribs facilitate entry of the projection into the hole in the jaw, and establish a tight fit when the projection is situated in the hole. In another embodiment, the projection fits into the hole with a snap fit, in which case the ribs may be eliminated.
The substantially rigid plastics layer can extend laterally beyond the longitudinal edges and ends of the plate portion of the metal element. However, in a preferred embodiment, the combination of the plate portion of the metal element and the aperture therein overlies substantially the entire substantially rigid plastics layer. The longitudinal edges of the plate portion extend past the projection on opposite sides of the projection, and the plate portion is preferably shaped so that the distance between the longitudinal edges on opposite sides of the projection is greater than the distance between the longitudinal edges adjacent the location of the clip.
By virtue of the foregoing features, and especially the use of a metal element in combination with a plastics projection, the grasping attachment can be made sufficiently small to be used with jaw instruments designed to extend through cannulae having very small internal diameters, e.g. 5 mm or smaller.
Other objects, details and advantages of the invention will be apparent from the following detailed description when read in conjunction with the drawings.